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Objective: To assess the consequences of infant botulism that result from Clostridium botulinum strains that produce 2 botulinum toxin serotypes, termed "bivalent."Study Design: Epidemiologic investigations used a standard questionnaire. Clostridium botulinum strains were isolated by standard methods. Botulinum neurotoxin (BoNT) serotypes and the relative amounts of toxins produced were identified using the standard mouse bioassay. BoNT subtypes and genomic locations were identified by DNA nucleotide sequencing.Results: Thirty bivalent cases of infant botulism occurred in the 45 years (1976-2020), representing 2.0% of all California infant botulism cases, in the 3 geographic regions of southern California, the southern Central Valley, and mid-northern California. Toxin serotype combinations were Ba (n = 22), Bf (n = 7), and Ab (n = 1). More patients with illness caused by bivalent C botulinum Ba and Bf strains needed endotracheal intubation at hospital admission, 60.0% (18/30), than did patients with illness caused by monovalent BoNT/B strains, 34.3% (152/443). The Cbotulinum Ba and Bf strains produced BoNT/B5 and either BoNT/A4 or /F2. The Ab strain produced BoNT/A2 and /B1. All toxin gene clusters were on plasmids.Conclusions: Infant botulism caused by bivalent Cbotulinum strains occurs sporadically and in diverse locations in California. Affected patients with bivalent Ba and Bf strains lacked distinguishing epidemiological features but appeared to be more severely paralyzed at hospital presentation than patients with illness caused by only BoNT/B. These bivalent strains produced BoNT subtypes A2, A4, B1, B5, and F2, and all toxin gene clusters were on plasmids. [ABSTRACT FROM AUTHOR]

Objective: Because Clostridium botulinum was isolated from powdered infant formula (PIF) fed to an infant in the United Kingdom who subsequently developed infant botulism and from unopened PIF from the same manufacturer, we tested PIF manufactured in the United States for the presence of clostridial spores. Study design: Thirty PIF ingested by 19 California infants with botulism within 4 weeks of onset of illness (48% of all patients fed PIF during study) in 2006-2007 were cultured anaerobically to isolate clostridia. All isolated clostridia were identified to the species level and enumerated with standard microbiologic and molecular methods. Results: Five of 30 (17%) PIF samples ingested by patients contained clostridial spores. Spores were also found in 7 of 9 (78%) market-purchased PIF samples. Clostridium sporogenes was isolated most frequently, followed by Clostridium butyricum and at least 10 other soil-dwelling clostridial species. No neurotoxigenic clostridia were isolated. The most probable number of clostridial spores in PIF ranged between 1.1 to >23 per 100 g. Conclusions: With the notable exception of production of botulinum neurotoxin, C sporogenes is physiologically comparable with proteolytic strains of C botulinum, and both share the same natural reservoir (soils and dust worldwide). The isolation of C sporogenes and potentially pathogenic clostridia from U.S.-manufactured PIF suggests that neurotoxigenic clostridial spores have the potential to be present in these products. [Copyright &y& Elsevier]